People like convenience -> Convenience leads to using a to-go cup -> using a to-go cup leads to it being thrown in the trash -> the cup thrown in the trash leads to more waste in our landfills -> more waste = bad news.

Check this out:

The Waste:

-Our single use paper cups are often times lined with plastic, which then as a result is not recyclable.

It sounds strange; I get it. However, it could just maybe save the planet a whole lot-a-bit.

Also: Better Flavor in a Mug

In going for convenience we miss the most important part of coffee; the coffee. Our paper cups are actually ever so slightly tainting the flavor of the coffee. When drinking out of paper you actually in turn get a small taste of paper in each sip.